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GeneralUpdate.Avalonia.Android Cookbook

This guide is for developers who need to integrate Android APK auto-update into their Avalonia applications. The goal is to complete the "check update → download APK → verify SHA256 → launch installer" workflow with minimal code.

Prerequisites

This guide assumes you already have an Avalonia project configured for Android target framework. If not, please refer to the Avalonia documentation first.

Update Flow​

① Version Check          ② Download APK          ③ Install
┌──────────┐          ┌──────────┐          ┌──────────────┐
│  Client  │──POST──→ │  Server  │          │  Android     │
│(Avalonia)│←─JSON─── │(Update   │          │  Package     │
└────┬─────┘          │ Service) │          │  Installer   │
     │                └────┬─────┘          └──────┬───────┘
     │  Server returns pkg info                    │
     │ ←────────────────────│                      │
     │                     │                       │
     │  GET /packages/app-v2.0.0.apk              │
     │ ────────────────────→│                      │
     │  APK file (Range supported)                │
     │ ←────────────────────│                      │
     │                     │                       │
     │  After SHA256 verification                  │
     │  launch Package Installer ────────────────→ │

Phase 1: Environment Setup​

Requirements​

ItemRequirementVerify
.NET SDK10.0+dotnet --version
Android SDKAPI 26+dotnet workload list (should include android)

NuGet Package​

dotnet add package GeneralUpdate.Avalonia.Android

Phase 2: FileProvider Configuration​

Add to AndroidManifest.xml:

<application>
    <provider
        android:name="androidx.core.content.FileProvider"
        android:authorities="${applicationId}.fileprovider"
        android:exported="false"
        android:grantUriPermissions="true">
        <meta-data
            android:name="android.support.FILE_PROVIDER_PATHS"
            android:resource="@xml/file_paths" />
    </provider>
</application>

Create Resources/xml/file_paths.xml:

<?xml version="1.0" encoding="utf-8"?>
<paths>
    <cache-path name="cache" path="update/" />
</paths>

Phase 3: Write Update Code​

using GeneralUpdate.Avalonia.Android;
using GeneralUpdate.Avalonia.Android.Models;

public class UpdateViewModel
{
    private IAndroidBootstrap? _bootstrap;

    public async Task CheckAndUpdateAsync()
    {
        var options = new AndroidUpdateOptions
        {
            FileProviderAuthority = "com.myapp.fileprovider"
        };

        _bootstrap = GeneralUpdateBootstrap.CreateDefault(options);

        _bootstrap.AddListenerDownloadProgressChanged += (_, e) =>
        {
            Console.WriteLine($"Download: {e.ProgressPercentage:F1}%");
        };

        var package = new UpdatePackageInfo
        {
            Version = "2.0.0",
            DownloadUrl = "http://10.0.2.2:5000/packages/app-v2.0.0.apk",
            Sha256 = "server-provided-sha256-hash",
            FileSize = 50_000_000,
            FileName = "app-v2.0.0.apk"
        };

        var checkResult = await _bootstrap.ValidateAsync(package, "1.0.0");
        if (!checkResult.UpdateFound)
        {
            Console.WriteLine("Already up to date.");
            return;
        }

        var downloadResult = await _bootstrap.DownloadAndVerifyAsync(package);
        if (!downloadResult.Success)
        {
            Console.WriteLine($"Download failed: {downloadResult.Message}");
            return;
        }

        if (Android.OS.Build.VERSION.SdkInt >= Android.OS.BuildVersionCodes.O)
        {
            var ctx = Android.App.Application.Context;
            var pm = ctx.PackageManager;
            if (pm != null && !pm.CanRequestPackageInstalls())
            {
                var intent = new Android.Content.Intent(
                    Android.Provider.Settings.ActionManageUnknownAppSources)
                    .SetData(Android.Net.Uri.Parse("package:" + ctx.PackageName));
                intent.AddFlags(Android.Content.ActivityFlags.NewTask);
                ctx.StartActivity(intent);
                return;
            }
        }

        var installResult = await _bootstrap.LaunchInstallerAsync(
            package, downloadResult.FilePath!);

        if (installResult.Success)
            Console.WriteLine("Installer launched. Confirm installation on device.");
    }
}

Phase 4: Start the Server​

git clone https://github.com/GeneralLibrary/GeneralUpdate-Samples.git
cd GeneralUpdate-Samples/src/Server
dotnet run

Server runs at http://localhost:5000. Use http://10.0.2.2:5000 from Android emulator to access host localhost.

Phase 5: End-to-End Verification​

  1. Place APK in Server/wwwroot/packages/
  2. Update wwwroot/packages/versions.json with version info
  3. Run the Avalonia Android app on emulator/device
  4. Observe: Check → Download → Verify → Install

Expected Output​

Checking for updates...
Update v2.0.0 found.
Downloading... 45% 1.2MB/s
Downloading... 100%
SHA256 verified.
Installer launched.

Next Steps​